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Model S volt question
- Thread starter Beasts
- Start date
E90alex
Active Member
It’s considered a “400V architecture” but specific pack voltage depending on model and battery size is somewhere in the ~350-400V range.
ucmndd
Well-Known Member
It doesn’t really change much. The truck itself and charging equipment can use smaller high voltage conductors, saving weight and materials, albeit at the need for more insulation and isolation considerations.
JzCastle
Member
The max battery voltage in the current Model S/X is 450V.
This is up from previous gen. 400V (100/90/85) or 350V (75).
The nominal voltage is 407V.
In real life this usually means means higher DC charging kW compared to previous models (depending on the DC charger and amps of course).
n2mb_racing
Active Member
Yup. current Model S/X has 110 cells in series, so max battery voltage should be 462V. They seem to have pushed the limits of the 400V architecture.
I have no idea how the Cybertruck is going to supercharge at the V3 and older superchargers. I think they all max out at 400V, which would mean needing to carry around a DC/DC converter on the truck. That would limit the peak charging rate. Unless they designed the battery to split in half for charging, like GM did.
I have no idea how the Cybertruck is going to supercharge at the V3 and older superchargers. I think they all max out at 400V, which would mean needing to carry around a DC/DC converter on the truck. That would limit the peak charging rate. Unless they designed the battery to split in half for charging, like GM did.
Speaking as a EE and from first principles (which probably means I'm wrong), there's a second-order effect: I^2-R losses.
Say one has two battery architectures: One at 400V with more cells in parallel, one at 800V with more cells in series, but both of these batteries have the same total number of cells, and therefore store the same amount of energy.
The power (i.e., the rate of discharge of the energy) would be the same for both batteries, where P = I*V. So, if the V for the overall battery is up by 2, then the current would be down by 2. And that would be for both discharging and charging the battery.
Now the tricky bit. Power dissipation in a wire with resistance R, goes as Current*Current*R. So, if the wire gauge isn't changed for the two batteries (not a great assumption, but let's go with it), the power dissipation in the wires would go down by a factor of four in the battery with 2X the voltage and X/2 the current.
This might not sound like a whole hill of beans, but take a 250 kW supercharger that's capable of charging an 800V system. (Or a 400V system, Superchargers have variable output voltage; it's part of how they work.)
At 250kW, the current at 400V would be 250e3/400 = 625A. At 800V, that would be 312.5A. Um. That's a lotta amps, and now you know why those Supercharger cables are as thick as they are and why they're often liquid cooled. But 625^2 = 390.63e3 amps-squared, and 312.5^2 = 96.65 amps-squared; and there's your power of 4 less power dissipation.
So, here's the deal: Copper is expensive. Big, thick copper cables, inside or outside of the car are more expensive than thinner cables. And now you know why High Tension Wires are such high voltage and, well, way up there to keep people from getting electrocuted.
So, what's likely is that Tesla's running somewhat thinner cable on the 800V architecture in order to save costs for them and for car buyers; and probably not so thin cables so that the power dissipation would be the same, thereby generating less waste heat when driving around or charging the car. Thus giving one a somewhat faster charging experience (less heat when charging means more energy into the battery) and somewhat more range (less energy going into heating wires as compared to moving the car).
First order effect? Nope. Second order effect? You betcha.
